Many scientists are convinced that the vast majority of the matter in the universe is invisible; perhaps containing five times more dark matter than ordinary matter. However, because dark matter does not reveal its presence by emitting any type of electromagnetic radiation, visible proof of its existence is elusive. Following the dark mater evidence chronologically, students explore matter and its interactions. They also learn about the scientists and technologies that made new discoveries possible. Finally they are introduced to the search for dark matter taking place at the Sanford Underground Research Facility.